<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <ul>
            <li v-for="item in arr">
                学生的姓名为:{{item.name}} , 年龄为:{{item.age}}
            </li>
        </ul>
        <div>该班级的平均年龄为:{{averageAge}}</div>
        <div>该班级的未成年人数为:{{count}}</div>
        <button @click="add">添加学生</button>
    </div>
    <script type="text/javascript" src="js/vue.js"></script>
    <script type="text/javascript">
        /*
              点击按钮, 发现了什么?
            */
        var vm = new Vue({
            el: '#app',
            computed: {
                averageAge: function() {
                    var total = 0
                    for (var i = 0; i < this.arr.length; i++) {
                        total += this.arr[i].age
                    }
                    return total / this.arr.length
                },
                count: function() {
                    var temp = 0
                    for (var i = 0; i < this.arr.length; i++) {
                        if (this.arr[i].age < 18) {
                            temp++
                        }
                    }
                    return temp
                }
            },
            data: {
                arr: [{
                    id: 1,
                    name: 'zhangsan',
                    age: 19
                }, {
                    id: 2,
                    name: 'lisi',
                    age: 8
                }, {
                    id: 3,
                    name: 'wangwu',
                    age: 15
                }]
            },
            methods: {
                add: function() {
                    var newObj = {
                        id: 4,
                        name: 'zhaoliu',
                        age: 13
                    }
                    this.arr.push(newObj)
                }
            }
        });
    </script>
</body>

</html>